Exemplary embodiments of the present invention relate to a semiconductor device, and more particularly, to a fuse of a semiconductor device and a method for fabricating the same, which can substantially prevent the failure of a repair fuse.
In a semiconductor memory device, if any one of a number of cells fails, the semiconductor memory device cannot properly function as a memory device, and therefore, is labeled as a bad product. However, if the entire semiconductor memory device is discarded because it is a bad product, even though a fail only occurs in a certain cell of the semiconductor memory device, an inefficient manufacturing yield results. Therefore, attempts have been made to improve the manufacturing yield by conducting a repair process in which a bad cell is replaced with a redundancy cell provided in advance in the semiconductor memory device, so that the entire semiconductor memory device can be restored to life. In order to replace the bad cell with the redundancy cell, the semiconductor memory device may have fuses. The repair process may be conducted through fuse blowing in which the fuse connected to the bad cell is cut by irradiating laser to the fuse.
FIGS. 1A through 1C are views illustrating a conventional fuse of a semiconductor device, wherein FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line I-I′ of FIG. 1A, and FIG. 1C is a cross-sectional view taken along the line II-II′ of FIG. 1A, showing a concern with the conventional fuse.
Describing a conventional fuse of a semiconductor device with reference to FIGS. 1A and 1B, a plurality of fuses 12 are formed on a substrate 11 having a predetermined structure, and a dielectric layer 14 which has a fuse box 15 is formed on the substrate 11 in such a way as to cover the fuses 12 while the fuse box 15 partially exposes the fuses 12 for a repair process.
In general, the fuses 12 are not formed through a separate process, and instead, portions of metal lines are used as the fuses 12. Recently, metal lines have been formed using copper (Cu), which has low specific resistance compared to aluminum (Al) or tungsten (W) and is therefore capable of improving signal transmission characteristics. Thus, the fuses 12 have also been formed by the metal lines formed of copper.
However, in the conventional art, as can be readily seen from FIG. 1C, a concern arises in that a repair fuse fail, in which a cut fuse 12 is electrically connected again (see the reference symbol ‘A’), is likely to occur. More specifically, a repair fuse fail may occur as a result of test circumstances, including temperature, humidity, voltage, etc., applied during a test such as an HAST (high acceleration stress test) performed after the repair process. Thus, performing such tests on a fuse of the conventional art means the repair yield and the reliability of the semiconductor device can deteriorate.
In more detail regarding the occurrence of a repair fuse fail, a conductive oxide is formed as the sides of a cut fuse 12 (that is, a repair fuse 12 that is cut so that it can repair a bad cell) are oxidated under test circumstances in which a temperature and a humidity are regulated. The cut fuse 12 can be electrically connected again as the formed conductive oxide gradually grows. Also, as migration, such as EM (electro migration) or SM (stress migration), occurs in the cut fuse 12 under test circumstances in which a voltage or a temperature is regulated, the cut fuse 12 can be electrically connected again.
In particular, because the copper constituting the fuse 12 is highly reactive with oxygen, in comparison to tungsten and aluminum, and is a material having great ion mobility, a repair fuse fail is likely to occur frequently due to oxidation and migration.